1. The Field of the Invention
The present invention relates to a transfer apparatus for transferring a semiconductor wafer. More particularly, the present invention relates to a transfer apparatus capable of transferring a semiconductor wafer in a narrow space by reducing a footprint.
2. Description of the Related Art
Generally, to fabricate devices such as a liquid crystal display (LCD) device, a plasma display device, or a semiconductor device, a cluster system has been frequently employed. A cluster system generally is used to indicate an apparatus for multiple process chambers comprising a transfer apparatus and a plurality of neighboring process modules. The cluster system is popular because the system can conduct multi-stage processes continuously and automatically.
For example, as disclosed in Japan Pat. No. 10-275848, a cluster system has an octagonal housing for an unloading chamber, and a transfer apparatus that rotates in the housing. Process modules may be set up at each side of the octagonal housing. The transfer apparatus removes a wafer from a load-lock cassette in a load-lock chamber, and loads the wafer into a process chamber of a process module. The wafer, after being processed in the process chamber, is removed from the transfer apparatus and loaded into the next process module, such as a load-lock module or the like.
The transfer apparatus used in the cluster system typically has a base, a first arm, a second arm and a handler. The first arm is positioned on the base and capable of rotation. The second arm is coupled to the top of the first arm and is also capable of rotation. The handler is coupled to the top of the second arm and is capable of rotation. Thus, the entire transfer apparatus is of a frog-leg type, composed of multiple joints adapted to rotate relative to one another.
Several problems exist with the transfer apparatus of the conventional cluster system as described above. Because wafers are handled horizontally, the cluster system arms require a wide space for horizontal rotation. Consequently, the transfer apparatus has a wide footprint and the entire working area of the apparatus is increased, reducing space efficiency per unit area. Such inefficient utilization of space additionally results in an increase in fabrication cost and inefficiency of automated transfer. Additionally, long arm length is required for covering the transfer distance, further limiting of processed amount thereby.
One approach to minimize the interference radius entails increasing the number of arms or pivots in the transfer apparatus, which raises concerns such as added mechanical complexity, reliability and maintenance.